Patch (or microstrip) antennas typically include a flat metal sheet mounted over a larger metal ground plane. The flat metal sheet usually has a rectangular shape, and the metal layers are generally separated using a dielectric spacer. The flat metal sheet has a length of approximately λ/2, and width can be optimized to provide a desired input impedance. Patch antennas can be configured to provide linear or circular polarization.
Dual-frequency patch antennas typically include two flat metal sheets mounted over a larger ground plane. Dual-frequency patch antennas exhibit a dual-resonant behavior in a single radiating structure, and they are often used in applications where increased bandwidth is needed or for operating at two separate sub-bands. Global navigation satellite system (GNSS) receivers often use right-handed circularly polarized (RHCP) dual-frequency patch antennas to receive GNSS signals at different frequencies (e.g., L1, L2, L2C, L3, L4, L5, and other GNSS frequencies).
Patch antennas are popular because of their simple design, low profile, light weight, and low cost. Improved designs are constantly sought to improve performance and further reduce cost.